Technical Field
The present invention relates to photovoltaic devices, and more particularly to devices and methods for fabricating photovoltaic devices with a textured electrode having improved properties.
Description of the Related Art
Solar panels employ photovoltaic cells to generate current flow. When a photon hits silicon, the photon may be transmitted through the silicon, reflected off the surface, or absorbed by the silicon if the photon energy is higher than the silicon band gap value. This generates an electron-hole pair and sometimes heat, depending on the band structure. The greater the absorption the greater the efficiency of the cell.
Textured substrate structures have been employed to increase the absorption efficiency. However, challenges arise at several points in the process. One such problem includes the formation of electrodes. An electrode deposition occurs by performing deep reactive ion etching (DRIE) the material followed by forming a thick layer of transparent electrode material to attempt to conform the electrode material to the shape of the underlying structure. DRIE is a highly anisotropic etch process making the formation of the textured surface template for subsequently deposited electrodes highly sensitive to thickness variations.
In addition, thinner material is preferred for electrodes conformally deposited on the textured substrate (with high aspect ratio) to maintain the textured profile. However, an electrode that is too thin results in sheet resistance problems (fill factor (FF) loss) and affects the efficiency of the solar cell. Further, laterally grown electrode materials can have different properties than planar grown materials. For example, laterally grown materials (on textured surfaces) have reduced transmittance as compared with planar grown materials.